There is conventionally known a transport method comprising: transporting a to-be-transported object to a destination to which the to-be-transported object shall be transported (referred to as a transport destination) in a horizontal posture by a transport robot having a hand comprising stationary (or fixed) clamp members which are capable of coming into contact with a periphery of a thin plate-shaped to-be-transported object, and a movable clamp member which is pressed into contact with the periphery of the to-be-transported object to thereby pinch the to-be-transported, object between the stationary clamp members and the movable clamp member; and thereafter lowering the hand in a state of having moved the movable clamp member backward to an unclamped position out of contact with the periphery of the to-be-transported object, thereby transferring the to-be-transported object onto a plurality of supporting pins disposed in the transport destination (see, for example, Patent Document 1). It is to be noted that the stationary clamp members and the movable member are formed of a material such as a resin, rubber, and the like which is lower in hardness than the to-be-transported object.
By the way when the transport robot has been put to uses to a certain degree, the position of the to-be-transported object that has been transferred onto the supporting pins at a transport destination will sometimes deviate out of the normal position of the to-be-transported object. The cause for the positional deviation was considered to be attributable to the control error of the transport robot. But due to diligent efforts by the inventors of this application, the cause has been found to be as follows. That is, since the stationary clamp members and the movable clamp member are formed of a material that is lower in hardness than that of the to-be-transported object, the clamp members, once they have been put to uses to a certain degree, give rise to dents due to wear. Then, after the to-be-transported object has been seated on the supporting pins as a result of lowering of the hand at the transport destination, that peripheral portion of the to-be-transported object which has got caught by (or engaged with) the dents of the stationary clamp members is pulled down by the subsequent lowering of the hand, and the peripheral portion on the opposite side will then, be lifted off from the supporting pins. Once the peripheral portion of the to-be-transported object has been driven out of the dents of the stationary clamp members, the to-be-transported object will be swung into movement on the supporting pins, thereby giving rise to the positional deviation.
As a solution, in order to prevent the positional deviation of the to-be-transported object, it is considered to replace the stationary clamp members before they give rise to dents. However, once the stationary clamp members are replaced, it is necessary to teach once again the transport position of the robot, or to confirm the position, resulting in time consumption. Therefore, frequent replacing of the stationary clamp members will result in lowering in the operating rate of the apparatus.